# git rev-parse -q --verify ab6f762f0f53162d41497708b33c9a3236d3609e^{commit} ab6f762f0f53162d41497708b33c9a3236d3609e already have revision, skipping fetch # git checkout -q -f -B kisskb ab6f762f0f53162d41497708b33c9a3236d3609e # git clean -qxdf # < git log -1 # commit ab6f762f0f53162d41497708b33c9a3236d3609e # Author: Sergey Senozhatsky # Date: Tue Mar 3 20:30:02 2020 +0900 # # printk: queue wake_up_klogd irq_work only if per-CPU areas are ready # # printk_deferred(), similarly to printk_safe/printk_nmi, does not # immediately attempt to print a new message on the consoles, avoiding # calls into non-reentrant kernel paths, e.g. scheduler or timekeeping, # which potentially can deadlock the system. # # Those printk() flavors, instead, rely on per-CPU flush irq_work to print # messages from safer contexts. For same reasons (recursive scheduler or # timekeeping calls) printk() uses per-CPU irq_work in order to wake up # user space syslog/kmsg readers. # # However, only printk_safe/printk_nmi do make sure that per-CPU areas # have been initialised and that it's safe to modify per-CPU irq_work. # This means that, for instance, should printk_deferred() be invoked "too # early", that is before per-CPU areas are initialised, printk_deferred() # will perform illegal per-CPU access. # # Lech Perczak [0] reports that after commit 1b710b1b10ef ("char/random: # silence a lockdep splat with printk()") user-space syslog/kmsg readers # are not able to read new kernel messages. # # The reason is printk_deferred() being called too early (as was pointed # out by Petr and John). # # Fix printk_deferred() and do not queue per-CPU irq_work before per-CPU # areas are initialized. # # Link: https://lore.kernel.org/lkml/aa0732c6-5c4e-8a8b-a1c1-75ebe3dca05b@camlintechnologies.com/ # Reported-by: Lech Perczak # Signed-off-by: Sergey Senozhatsky # Tested-by: Jann Horn # Reviewed-by: Petr Mladek # Cc: Greg Kroah-Hartman # Cc: Theodore Ts'o # Cc: John Ogness # Signed-off-by: Linus Torvalds # < /opt/cross/kisskb/arcompact-buildroot-2015.08.1/bin/arc-buildroot-linux-uclibc-gcc --version # < /opt/cross/kisskb/arcompact-buildroot-2015.08.1/bin/arc-buildroot-linux-uclibc-ld --version # < git log --format=%s --max-count=1 ab6f762f0f53162d41497708b33c9a3236d3609e # < make -s -j 24 ARCH=arc O=/kisskb/build/linus_axs101_defconfig_arcompact CROSS_COMPILE=/opt/cross/kisskb/arcompact-buildroot-2015.08.1/bin/arc-buildroot-linux-uclibc- axs101_defconfig # Added to kconfig CONFIG_INITRAMFS_SOURCE="" # < make -s -j 24 ARCH=arc O=/kisskb/build/linus_axs101_defconfig_arcompact CROSS_COMPILE=/opt/cross/kisskb/arcompact-buildroot-2015.08.1/bin/arc-buildroot-linux-uclibc- help # make -s -j 24 ARCH=arc O=/kisskb/build/linus_axs101_defconfig_arcompact CROSS_COMPILE=/opt/cross/kisskb/arcompact-buildroot-2015.08.1/bin/arc-buildroot-linux-uclibc- olddefconfig # make -s -j 24 ARCH=arc O=/kisskb/build/linus_axs101_defconfig_arcompact CROSS_COMPILE=/opt/cross/kisskb/arcompact-buildroot-2015.08.1/bin/arc-buildroot-linux-uclibc- /kisskb/src/drivers/gpu/drm/drm_dp_mst_topology.c: In function 'drm_dp_mst_dsc_aux_for_port': /kisskb/src/drivers/gpu/drm/drm_dp_mst_topology.c:5497:9: warning: missing braces around initializer [-Wmissing-braces] struct drm_dp_desc desc = { 0 }; ^ /kisskb/src/drivers/gpu/drm/drm_dp_mst_topology.c:5497:9: warning: (near initialization for 'desc.ident') [-Wmissing-braces] /kisskb/src/net/ipv4/tcp_input.c: In function 'tcp_data_queue': /kisskb/src/net/ipv4/tcp_input.c:4398:49: warning: array subscript is above array bounds [-Warray-bounds] tp->selective_acks[i-1] = tp->selective_acks[i]; ^ Completed OK # rm -rf /kisskb/build/linus_axs101_defconfig_arcompact # Build took: 0:01:11.492051